Pipelines being used in the oil and gas field are often subject to large strain in the form of stress, pressure and temperature variations. Because of this the pipelines are frequently inspected for displacements, cracks or possible leaks. A known method for performing such inspections is x-ray photographing of the pipeline. Different systems performing such inspections are available on the market.
Flexible pipelines are built to stand the abovementioned strains. A usual structure of flexible pipelines is a multi-layer system of steel pipes with polymer materials between them. The polymer layers include a pressure sheet which hinders diffusion and leakage of the pipeline content out into the environment. It is also demanded that the pressure sheet is able to move relatively freely in relation to the steel pipes, thus not to be subject to unnecessary strain when the pipeline moves. Between the pressure sheet and the steel pipes an anti-creep sheet is often placed in order to keep the pressure sheet from fastening to the steel layers. In the ends of each pipe part a coupling part is comprised which among other things may comprise a sealing or a packing ring providing a seal between the pipelines and also between the pressure sheets.
A problem relating to the abovementioned structure is that the pressure sheet has shown a tendency to contract and thus be drawn away from the sealing ring, making the pipeline leaky.